I have had the opposite happen to me. I was at a company Christmas party and I was asked if I was the mother of my boyfriend. He is ten years younger than me. It was depressing to hear, but I tried to let it go in one ear and out the other. I have been asked if I am his mother more than once. Luckily, I have a pretty good self concept, and I don't let what people say affect me that much, especially strangers. Add to the mix, that I am obese and he has the perfect physique and is not overweight.
Keep your chin up and be proud of who you are. I am sure you have wonderful and unique qualities.